[Okta Webinar] Learn how to a build a cloud-first strategyRegister Now

x
?
Solved

Array of TextFields hangs applet

Posted on 1997-06-20
2
Medium Priority
?
377 Views
Last Modified: 2006-11-17
I've created an array of TextFields, to simplify field-population in an applet.  In my init() method, I can 'setText()',  get 'myTextField[i].length()', whatever.  Any TextField method works as advertized, so I've allocated and instantiated it properly.  But once my event handler calls *any other method in my class*, 'myTextField[i]' becomes a black hole: the debugger (visual cafe's) won't show its
value and the execution seems to fix on any line with a reference to it (as if it was in an infinite loop).  Any TextField method, called from any of my methods,  (i.e.:"myTextField[0].setText()" ) produces the same
result.  If I hadn't declared it as "global" to my class, I'd suspect scope-trouble.  What am I doing wrong?!!

Sample:

public class URLApplet extends Applet {

    int i;
    java.awt.TextField myTextField[];

 public void init() {
  super.init();

        TextField myTextField[] = new TextField[8];

        for (i=0; i < myTextField.length; i++) {       //works just fine
           myTextField[i] = new TextField();
        }
        myTextField[0].reshape(156,36,331,23);       //works just fine
        //...etc...

        for (i=0; i < myTextField.length; i++) {         //works just fine
            add(myTextField[i]); //works just fine
        }
        myTextField[0].setText("succeeds");             //works just fine, here!!!
 }

 private void clearScreen() {

        for (i=0; i < 6; i++) {
           myTextField[i].setText(" ");                       //*hangs here*
        }
 }

 public void populateTextFields() {
     int token = 0;
     try {
         URL urlObject = new URL("http://etc.com/cgi-bin/foo" + myTextField[8].getText());                                     //*hangs here*
            URLConnection agent = urlObject.openConnection();
            InputStreamReader(agent.getInputStream());
            StreamTokenizer stDealer = new
StreamTokenizer(agent.getInputStream());
            int tokenType = st.nextToken();
            int elems = myTextField[0].length               //*hangs here*
            for (i=0; i < elems; i++) {
//*hangs here*
                myTextField[i].setText(st.sval);               //*hangs here*
                tokenType = st.nextToken();
            } catch { blah, blah, blah;}

 public boolean action (Event e, Object o) {

     if (e.target instanceof Button || e.target instanceof TextField) {
     //if (e.target instanceof Button) {
   try {
       clearScreen();                //*never comes back*
       stopWatch();
       populateTextFields();         //*never comes back*

          } catch (Exception x) {
             System.out.print(x);
            }
        }
    return true;
    }
}

0
Comment
Question by:pwicks
2 Comments
 

Accepted Solution

by:
jaiger earned 300 total points
ID: 1221878
sounds to me like a synchronization problem.  

you may not be dealing with an infinite loop but actually a thread blocking on some sort of mutex semaphore.

try wrapping all references to the text field array, after init(), in synchronized blocks.  

you could also try using a Vector instead of an array (?) since Vectors tend to be somewhat synchronized.
0
 

Author Comment

by:pwicks
ID: 1221879
This synchronization notion is worth noting, but two other responses have arrived this morning via E-mail indicating that I had allocated a second array when I thought I was instantiating the original array:

java.awt.TextField myTextField[];//declares array (method global)
TextField myTextField[] = new TextField[8]; //declares (redundantly) and initializes, but local to the init() method!

/* -- this is a *second* array. Since I hadn't initialized the original array, I was trying to use an array which was null. This caused the "black hole" effect, although I expected better of Java. Perhaps this is where syncronization would help.
it should read: */

myTextField[] = new TextField[8]; //instantiates original array.

Problem solved. Lesson learned. Thanks to all who responded and good luck to all who this "object lesson" may help.
0

Featured Post

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction This article is the first of three articles that explain why and how the Experts Exchange QA Team does test automation for our web site. This article explains our test automation goals. Then rationale is given for the tools we use to a…
Basic understanding on "OO- Object Orientation" is needed for designing a logical solution to solve a problem. Basic OOAD is a prerequisite for a coder to ensure that they follow the basic design of OO. This would help developers to understand the b…
This video teaches viewers about errors in exception handling.
How to fix incompatible JVM issue while installing Eclipse While installing Eclipse in windows, got one error like above and unable to proceed with the installation. This video describes how to successfully install Eclipse. How to solve incompa…
Suggested Courses
Course of the Month18 days, 23 hours left to enroll

834 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question